U.S. patent application number 11/824691 was filed with the patent office on 2009-01-08 for fixed-point packoff element with primary seal test capability.
This patent application is currently assigned to Stinger Wellhead Protection, Inc.. Invention is credited to Danny Lee Artherholt.
Application Number | 20090008100 11/824691 |
Document ID | / |
Family ID | 40220558 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090008100 |
Kind Code |
A1 |
Artherholt; Danny Lee |
January 8, 2009 |
Fixed-point packoff element with primary seal test capability
Abstract
A fixed-point packoff element for a full-bore pressure isolation
tool supports a primary seal and a test seal to permit the primary
seal to be tested by injecting test fluid through a side port of a
tubing head spool before the pressure isolation tool is rigged up
for a well stimulation procedure.
Inventors: |
Artherholt; Danny Lee;
(Asher, OK) |
Correspondence
Address: |
NELSON MULLINS RILEY & SCARBOROUGH, LLP
1320 MAIN STREET, 17TH FLOOR
COLUMBIA
SC
29201
US
|
Assignee: |
Stinger Wellhead Protection,
Inc.
|
Family ID: |
40220558 |
Appl. No.: |
11/824691 |
Filed: |
July 2, 2007 |
Current U.S.
Class: |
166/337 ;
166/90.1 |
Current CPC
Class: |
E21B 33/04 20130101 |
Class at
Publication: |
166/337 ;
166/90.1 |
International
Class: |
E21B 33/02 20060101
E21B033/02 |
Claims
1. A fixed-point packoff element, comprising: at least one O-ring
groove adapted to receive an O-ring that provides a primary seal
between the fixed-point packoff element and a seal bore below a
side port of a tubing head spool into which the fixed-point packoff
element is inserted; and at least one O-ring groove adapted to
receive an O-ring that provides a test seal in a seal bore of the
tubing head spool above the side port of the tubing head spool.
2. The fixed-point packoff element as claimed in claim 1 further
comprising a bottom end having a bevel that mates with a bit guide
of the tubing head spool.
3. The fixed-point packoff element as claimed in claim 2 further
comprising an O-ring groove in the bevel, adapted to receive an
O-ring that inhibits well stimulation fluid from migrating between
the bevel and the bit guide.
4. The fixed-point packoff element as claimed in claim 1 comprising
three O-ring grooves respectively adapted to receive O-rings that
provide the primary seal.
5. The fixed-point packoff element as claimed in claim 1 comprising
four O-ring grooves respectively adapted to receive O-rings that
provide the primary seal.
6. The fixed-point packoff element as claimed in claim 1 comprising
two O-ring grooves respectively adapted to receive an O-ring that
provides the test seal.
7. The fixed-point packoff element as claimed in claim 1 further
comprising a test fluid groove machined into a sidewall of the
fixed-point packoff element between the at least one O-ring groove
adapted to receive the O-ring that provides the primary seal and
the O-ring groove adapted to receive the O-ring that provides the
test seal.
8. The fixed-point packoff element as claimed in claim 1 wherein a
top end of the fixed-point packoff element comprises a pin thread
that cooperates with a box thread of a high-pressure mandrel to
connect the fixed-point packoff element to the high-pressure
mandrel.
9. The fixed-point packoff element as claimed in claim 8 further
comprising a seal pin above the pin thread, the seal pin
cooperating with an O-ring received in an O-ring groove above the
box thread of the high-pressure mandrel to provide a seal to
inhibit well stimulation fluid from migrating into the pin thread
and the box thread.
10. The fixed-point packoff element as claimed in claim 1 further
comprising a central passage through the fixed-point packoff
element that is at least as large as a diameter of a production
tubing supported by the tubing head spool.
11. The fixed-point packoff element as claimed in claim 1 wherein
an outer diameter of the fixed-point packoff element received in
the seal bore below the side port is smaller than an outer diameter
of the fixed point packoff element received in the seal bore above
the side port.
12. A fixed-point packoff element for a high-pressure mandrel of a
full-bore pressure isolation tool, comprising: a hollow cylindrical
body with a top end and a bottom end and a central passage that
extends from the top end to the bottom end; at least one O-ring
groove in an outer periphery of the hollow cylindrical body,
adapted to receive an O-ring that provides a primary seal between
the fixed-point packoff element and a seal bore below a side port
of a tubing head spool into which the fixed-point packoff element
is inserted; and at least one O-ring groove in the outer periphery
of the hollow cylindrical body, adapted to receive an O-ring that
provides a test seal in a seal bore of the tubing head spool above
the side port of the tubing head spool.
13. The fixed-point packoff element as claimed in claim 12 wherein
an outer diameter of the outer periphery of the hollow cylindrical
body with the at least one O-ring groove that receives the O-ring
for providing the primary seal is the same as an outer diameter of
the outer periphery of the hollow cylindrical body with the at
least one O-ring groove that receives the O-ring for providing the
test seal.
14. The fixed-point packoff element as claimed in claim 12 wherein
an outer diameter of the outer periphery of the hollow cylindrical
body with the at least one O-ring groove that receives the O-ring
for providing the primary seal is smaller than an outer diameter of
the outer periphery of the hollow cylindrical body with the at
least one O-ring groove that receives the O-ring for providing the
test seal.
15. The fixed-point packoff element as claimed in claim 12
comprising three O-ring grooves for respectively receiving O-ring
seals for providing the primary seal.
16. The fixed-point packoff element as claimed in claim 12
comprising four O-ring grooves for respectively receiving O-ring
seals for providing the primary seal.
17. The fixed-point packoff element as claimed in claim 12
comprising two O-ring grooves for respectively receiving O-ring
seals for providing the test seal.
18. A fixed-point packoff element for a high-pressure mandrel of a
full-bore pressure isolation tool, comprising: a hollow cylindrical
body having a threaded top end for connection to a high-pressure
mandrel of the full-bore pressure isolation tool, a bottom end with
a bevel adapted to mate with a bit guide in a tubing head spool,
and a central passage that extends from the top end to the bottom
end in fluid communication with the high-pressure mandrel; a
plurality of O-ring grooves in an outer periphery of the hollow
cylindrical body, respectively adapted to receive an O-ring that
provides a primary seal between the fixed-point packoff element and
a seal bore below a side port of a tubing head spool into which the
fixed-point packoff element is inserted; and at least one O-ring
groove in the outer periphery of the hollow cylindrical body,
adapted to receive an O-ring that provides a test seal in a seal
bore of the tubing head spool above the side port of the tubing
head spool.
19. The fixed-point packoff element as claimed in claim 18 further
comprising a test fluid groove in an outer periphery of the hollow
cylindrical body between the plurality of O-ring grooves and the at
least one O-ring groove.
20. The fixed-point packoff element as claimed in claim 18 further
comprising an O-ring groove in the bevel adapted to receive an
O-ring for providing a fluid seal between the bevel and the bit
guide when the fixed-point packoff element is seated on the bit
guide.
Description
FIELD OF THE INVENTION
[0001] This invention relates in general to hydrocarbon well
stimulation equipment and, in particular, to a fixed-point packoff
element with primary seal test capability.
BACKGROUND OF THE INVENTION
[0002] The inventions of Assignee's pressure isolation tools that
provide full-bore access to a casing of the well have
revolutionized the well stimulation industry. Full-bore isolation
tools seal or "pack off" at a fixed-point above a bit guide in a
seal bore of a tubing head spool that supports a production casing
in the well, and permit full bore access to the production
casing.
[0003] A fixed-point packoff element provides a high pressure seal
in the tubing head spool seal bore. The full-bore access pressure
isolation tools permit stimulation fluid to be pumped into a well
at pressures of 15,000+ psi and rates of 300+ bbl/minute. As well,
the fixed-point packoff element permits any downhole tool to be run
into the casing so that multiple production zones can be stimulated
without unrigging frac irons or the full-bore pressure isolation
tool.
[0004] Since stimulation fluids are commonly pumped into the well
at fluid pressures of at least 10,000 psi, the packoff element must
provide a very reliable high pressure seal. In order to do so, the
packoff element must have an outer diameter that is not more than
about 0.005''-0.030'' smaller than an inner diameter of the tubing
head spool seal bore. As is well understood in the art, an exact
inner diameter of a tubing head spool seal bore is not always known
with certainty. Consequently, full-bore pressure isolation tools
have been rigged up as follows: a packoff element is selected based
on a best knowledge of an inner diameter of the tubing head spool
seal bore; the packoff element is run it and set; frac irons are
hooked up to the full-bore pressure isolation tool and the well is
pumped up to test pressure; a tubing head spool side port is
monitored for pressure leaks; and, if the packoff element does not
contain the test pressure, the test pressure is bled off, the frac
irons are disconnected, the pressure isolation tool is removed from
the wellhead and the packoff element is changed for a next larger
diameter, typically about 0.015'' larger. The entire process is
then repeated. This can be a time consuming and expensive
process.
[0005] There therefore exists a need for a fixed-point packoff
element with a primary seal test capability to permit primary seal
testing prior to rigging up the pressure isolation tool for a well
stimulation operation.
SUMMARY OF THE INVENTION
[0006] It is therefore an object of the invention to provide a
fixed-point packoff element with a primary seal test
capability.
[0007] The invention therefore provides a fixed-point packoff
element, comprising: at least one O-ring groove adapted to receive
an O-ring that provides a primary seal between the fixed-point
packoff element and a seal bore below a side port of a tubing head
spool into which the fixed-point packoff element is inserted; and
at least one O-ring groove adapted to receive an O-ring that
provides a test seal in a seal bore of the tubing head spool above
the side port of the tubing head spool.
[0008] The invention further provides a fixed-point packoff element
for a high-pressure mandrel of a full-bore pressure isolation tool,
comprising: a hollow cylindrical body with a top end and a bottom
end and a central passage that extends from the top end to the
bottom end; at least one O-ring groove in an outer periphery of the
hollow cylindrical body, adapted to receive an O-ring that provides
a primary seal between the fixed-point packoff element and a seal
bore below a side port of a tubing head spool into which the
fixed-point packoff element is inserted; and at least one O-ring
groove in the outer periphery of the hollow cylindrical body,
adapted to receive an O-ring that provides a test seal in a seal
bore of the tubing head spool above the side port of the tubing
head spool.
[0009] The invention yet further provides a fixed-point packoff
element for a high-pressure mandrel of a full-bore pressure
isolation tool, comprising: a hollow cylindrical body having a
threaded top end for connection to a high-pressure mandrel of the
full-bore pressure isolation tool, a bottom end with a bevel
adapted to mate with a bit guide in a tubing head spool, and a
central passage that extends from the top end to the bottom end in
fluid communication with the high-pressure mandrel; a plurality of
O-ring grooves in an outer periphery of the hollow cylindrical
body, respectively adapted to receive an O-ring that provides a
primary seal between the fixed-point packoff element and a seal
bore below a side port of a tubing head spool into which the
fixed-point packoff element is inserted; and at least one O-ring
groove in the outer periphery of the hollow cylindrical body,
adapted to receive an O-ring that provides a test seal in a seal
bore of the tubing head spool above the side port of the tubing
head spool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Having thus generally described the nature of the invention,
reference will now be made to the accompanying drawings, in
which:
[0011] FIG. 1 is a schematic cross-sectional diagram of one
embodiment of a fixed-point packoff element in accordance with the
invention;
[0012] FIG. 2 is a schematic cross-sectional diagram of another
embodiment of the fixed-point packoff element in accordance with
the invention;
[0013] FIG. 3 is a schematic cross-sectional diagram of the
fixed-point packoff element shown in FIG. 1 packed off in a seal
bore of a tubing head spool of a wellhead;
[0014] FIG. 3a is a schematic cross-sectional diagram of an
exploded view of the tubing head spool and fixed-point packoff
element shown in FIG. 3;
[0015] FIG. 4 is a schematic cross-sectional diagram of the
fixed-point packoff element shown in FIG. 2 packed off in a seal
bore of a tubing head spool of a wellhead; and
[0016] FIG. 4a is a schematic cross-sectional diagram of an
exploded view of the tubing head spool and the fixed-point packoff
element shown in FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The invention provides a fixed-point packoff element for a
full-bore pressure isolation tool that permits primary seal testing
to facilitate rig up for a well stimulation procedure. The
fixed-point packoff element provides a secondary seal in the seal
bore above side ports of a tubing head spool. This permits test
fluid to be pumped through a side port of the tubing head spool to
determine whether a primary seal has been achieved. If the
fixed-point packoff element retains the test fluid, a primary seal
has been achieved and it can be assumed with a high level of
confidence that the fixed-point packoff element will provide a
reliable pressure seal at full well stimulation fluid pressure.
[0018] FIG. 1 is a schematic cross-sectional diagram of one
embodiment of a fixed-point packoff element 10 in accordance with
the invention. The fixed-point packoff element 10 is a hollow
cylindrical body connected to a high-pressure mandrel 12 of a
full-bore pressure isolation tool (not shown) that is well known in
the art. A box thread 14 of the high-pressure mandrel 12 cooperates
with a pin thread 16 of the fixed-point packoff element 10 to
connect the fixed-point packoff element 10 to the high-pressure
mandrel 12. An O-ring groove 17 receives an O-ring 18 that provides
a high-pressure seal between the fixed-point packoff element 10 and
the high-pressure mandrel 12 to inhibit well stimulation fluids
from migrating into the threads 14, 16. At least one O-ring groove,
three in this example, 15a, 15b and 15c respectively receive
O-rings 20a, 20b and 20c to provide a high-pressure primary seal in
a seal bore of a tubing head spool, as will be explained below with
reference to FIGS. 3 and 3a. An optional O-ring groove 21 receives
an O-ring 22 that provides a fluid seal between a bit guide of the
tubing head spool and the fixed-point packoff element 10. In this
embodiment, a test fluid groove 24 is machined into a periphery of
the fixed-point packoff element 10. The test fluid groove 24 is
optional. At least one O-ring groove, in this example two O-ring
grooves 25a and 25b respectively receive O-rings 26a, 26b, that
provide a test seal above side ports of the tubing head spool, as
will also be explained below with reference to FIGS. 3 and 3a.
[0019] In this embodiment a top end 28 of the fixed-point packoff
element 10 provides a polished seal pin 30 that seals against the
O-ring 18. As will be understood by those skilled in the art, a
seal bore could be provided in the high-pressure mandrel 12 above
the box thread 14, and the O-ring 18 could be carried in an O-ring
groove machined in the top end 28 of the packoff element 10. In
this embodiment, a bottom end 32 of the packoff element 10 is
beveled 34 to mate with the bit guide of the tubing head spool, as
will also be explained below with reference to FIG. 3a. As is
apparent, a central passage 36 through the fixed-point packoff
element 10 has an inner diameter equal to an inner diameter of a
central passage 38 of the high-pressure mandrel 12. The inner
diameter of the central passage 36 is at least as large as an inner
diameter of a production casing supported by a tubing head spool
into which the fixed-point packoff element is inserted.
[0020] FIG. 2 is a schematic cross-sectional diagram of another
embodiment of a fixed-point packoff element 50 in accordance with
the invention. The fixed packoff element 50 is substantially
identical to the fixed packoff element 10 described above except
that the hollow cylindrical body is designed for a tubing head
spool in which the seal bore above the bit guide is of a smaller
diameter than a seal bore above the side ports of the tubing head
spool, as will be explained below in more detail with reference to
FIGS. 4 and 4a.
[0021] The fixed-point packoff element 50 is connected to the box
threads 14 by a pin thread 52. The top end 54 includes a seal pin
56 that seals against the O-ring 18, as explained above with
reference to FIG. 1. At least one O-ring groove, in this example 4
O-ring grooves 61a, 61b, 61c and 61d respectively receive O-rings
62a, 62b, 62c and 62d that provide the primary seal. In this
embodiment the bottom end 58 includes a bevel 60 that mates with
the bit guide, as will be explained below with reference to FIG.
4a. An optional O-ring groove 63 receives an O-ring 64 that
provides a seal between the bevel 60 and the bit guide to inhibit
well stimulation fluid from migrating between the bevel 60 and the
bit guide.
[0022] An optional test fluid groove 66 is machined around an outer
periphery of the fixed-point packoff element 50. A test seal is
provided by at least one O-ring received in at least one O-ring
groove. In this example, two O-ring grooves 65i a and 65b
respectively receive O-rings 68a, 68b that provide the test seal. A
central passage 70 of the fixed-point packoff element 50 has the
same inner diameter as the central passage 38 of the high-pressure
mandrel 12. The inner diameter of the central passage 70 is at
least as large as an inner diameter of a production casing
supported by a tubing head spool into which the fixed-point packoff
element is inserted. An outer diameter of the fixed-point packoff
element 50 increases at a shoulder 72 to conform to an inner
diameter of the tubing head spool, as will be explained below with
reference to FIG. 4a.
[0023] FIG. 3 is a schematic cross-sectional diagram of the
fixed-point packoff element 10 shown in FIG. 1 packed off in a seal
bore of a tubing head spool 100 of a wellhead 102. The mandrel 12
of a full-bore isolation tool 104 (only a base of which is shown)
has been stroked down through a blowout preventer (BOP) 106 until
the fixed-point packoff element 10 rests against the bit guide of
the tubing head spool 100. The tubing head spool 100 shown in this
example has two side ports 108a, 108b. The side port 108a is sealed
with the side port plug 110, well known in the art. The side port
108b is equipped with the side port valve 112, also well known in
the art. A test fluid line 114 is connected to the side port 112 so
that test fluid can be pumped into the test fluid groove 24 to test
the primary seal of the fixed-point packoff element 10, as will be
explained below with reference to FIG. 3a.
[0024] FIG. 3a is a schematic cross-sectional diagram of an
exploded view of the fixed-point packoff element 10 shown in FIG.
3. As can be seen, the bevel 34 on the bottom end 32 of the
fixed-point packoff element 10 mates with a bit guide 116 of the
tubing head spool 100. The O-rings 20a, 20b and 20c provide the
primary seal between a seal bore 118 of the tubing head spool 100
and the fixed-point packoff element 10. The O-ring 22 provides a
fluid seal between the bevel 34 and the bit guide 116. As also
explained above, the test seal is provided by the O-rings 26a and
26b. Test fluid 120 is injected through the test fluid line 114 and
the side port 112 to fill a space defined by the side port valve,
the test groove 24 and a space between a sidewall of the
fixed-point packoff element 10 and the tubing head spool seal bore
118. The test fluid may be any appropriate fluid, including
hydraulic oil, water, air, etc. After the space is filled, the test
fluid is pumped to a pressure at or near a rated pressure of the
side port valve 112. If the test fluid pressure is maintained by
the fixed-point packoff element 10, a primary seal has been
achieved and rig up can continue with a high degree of confidence
that the fixed-point packoff element will provide a reliable seal
at full well stimulation fluid pressure.
[0025] If the primary seal is not achieved, either the primary seal
O-rings 20a, 20b, 20c or the test seal O-rings 26a, 26b have failed
to seal against the seal bore 118. Consequently, the mandrel 12 is
stroked backup through the BOP 106 and the full-bore pressure
isolation tool 104 is removed from the BOP 106, so that the
fixed-point packoff element 10 can be changed for one of a slightly
larger diameter. The new fixed-point packoff element 10 is then
stroked down through the BOP and landed against the bit guide 116.
The primary seal test is then repeated. All of this is accomplished
before frac irons or other well stimulation equipment is connected
to the full-bore pressure isolation tool 104. Uncertainty is
therefore reduced and time is potentially saved.
[0026] FIG. 4 is a schematic cross-sectional diagram of the
fixed-point packoff element 50 shown in FIG. 2 packed off in a seal
bore of a tubing head spool 200 of a wellhead 202. The mandrel 12
of the full-bore pressure isolation tool 104 (only the base of
which is shown) has been stroked down through the BOP 106 until the
fixed-point packoff element 50 rests against the bit guide of the
tubing head spool 200. The tubing head spool 200 shown in this
example has two side ports 208a, 208b. The side port 208a is sealed
by a side port plug 210. The side port 208b is equipped with a side
port valve 212, also well known in the art. A test pressure line
214 is connected to the side port 212 so that test fluid can be
pumped in to test the primary seal of the fixed-point packoff
element 50, as will be explained below with reference to FIG.
4a.
[0027] FIG. 4a is a schematic cross-sectional diagram of an
exploded view of the fixed-point packoff element 50 shown in FIG.
4. As can be seen, the bevel 60 on the bottom end 58 of the
fixed-point packoff element 50 mates with a bit guide 216 of the
tubing head spool 200. The O-rings 62a, 62b, 62c and 62d provide
the primary seal between a seal bore 218 of the tubing head spool
200 and the fixed-point packoff element 50. The optional O-ring 64
provides a fluid seal between the bevel 60 and the bit guide 216.
In this embodiment, the seal bore is stepped at 220 to a larger
diameter, and the outer diameter of the fixed-point packoff element
50 increases at the shoulder 72 to conform to an inner diameter of
the seal bore 222 of the tubing head spool 200. The test seal is
provided by the O-rings 68a and 68b which seal against the seal
bore 222.
[0028] Test fluid 224 is injected through the test fluid line 214
and the side port valve 212 to fill a space defined by the side
port valve 212 and the sidewall of the fixed-point packoff element
between O-rings 62a and 68b. As explained above, the test fluid may
be any appropriate fluid, such as hydraulic oil, water, air, etc.
After the space is filled, the test fluid is pumped to a pressure
at or near a rated pressure of the side port valve 212. If the test
pressure is maintained by the fixed-point packoff element 50, a
primary seal has been obtained and rig up can continue with a high
degree of confidence that the fixed-point packoff element will
provide a reliable seal at full well stimulation fluid pressure. As
explained above, if the test pressure is lost, the fixed-point
packoff element 50 is changed and the test seal is re-tested.
[0029] While two embodiments of the fixed-point packoff element in
accordance with the invention have been described, it should be
understood that those embodiments are exemplary only.
[0030] The scope of the invention is therefore intended to be
limited solely by the scope of the appended claims.
* * * * *